Currently, multiple-series transmitting devices each having a plurality of transmitting systems such as transmission diversity devices and MIMO (Multiple-Input and Multiple-Output) devices have been designed using multiple-series amplifying devices.
Multiple-series amplifying devices include multiple series of amplifiers which are formed in parallel so as to input and output signals individually. Each of multiple series of amplifiers includes a plurality of semiconductor amplifying elements which are driven in parallel so as to amplify signals.
Multiple-series amplifying devices demonstrate high-output performance since a plurality of semiconductor amplifying elements are driven in parallel, while multiple-series amplifying devices of a Doherty-type demonstrate high efficiencies since a plurality of semiconductor amplifying elements are driven in parallel.
It is possible to design an amplifier in which a first amplifying element and a second amplifying element, serving as the last stage of amplification power elements, are disposed between an input terminal and an output terminal, wherein the first amplifying element and the second amplifying element are formed on a single semiconductor chip (see Patent Literature Document 1).
Additionally, it is possible to design another amplifier in which an output signal of a digital modulator is input to a power amplifying device and distributed into n signals via an n-distributor; n signals are subjected to n input phase shifters having different phase shifts and then amplified with a power amplifier; n signals are subjected to n output phase shifters so that their phases will match each other; subsequently, n signals are combined together with an n-combiner so as to output a combined signal via an output terminal (see Patent Literature Document 2).